Field of the Invention
The present invention relates to a door impact beam and a manufacturing method thereof and, more particularly, to a door impact beam for supplementing the strength of an automotive door and a method of manufacturing the door impact beam.
Description of Related Art
Automotive doors are manufactured by coupling panels to both sides of door frames having empty compartments at the center portions, so door impact beams are disposed to supplement the strength for the empty compartments inside the door frames.
A door impact beam is plastically deformed by a load laterally applied to an automotive door, thereby absorbing impact energy and preventing a passenger from being injured.
Door impact beams are generally formed in hollow pipe shapes having a circular or elliptical cross-section, and brackets are used to connect both end portions of the door impact beams and a door frame.
FIG. 1 is a view depicting a coupling relationship between a door frame 1 and a door impact beam 10, FIG. 2 is an enlarged view depicting a joint between an end portion of the door impact beam 10 and the door frame 1, and FIG. 3 is a view depicting a coupling relationship among the door impact beam 10 cut along line A-A in FIG. 1, an external panel 2, and a sealer 3.
As shown in FIG. 1 to FIG. 3, a plurality of brackets 20 are coupled to the door impact beam 10 of the prior art. In detail, the door impact beam 10 is coupled to the door frame 1 through a first bracket 21 at a first end portion and a second bracket 22 at a second end portion, and the sealer 3 is prevented from separating out of the area between the external panel 2 and the door impact beam 10 by a third bracket 23.
That is, the third bracket 23 is disposed at the portion where the gap between the external panel 2 and the door impact beam 10 is large to decrease the gap so that the external panel 2 and the door impact beam 10 maintain a predetermined gap therebetween, preventing the sealer 3 from separating.
The door impact beam 10, the first bracket 21, the second bracket 22, and the third bracket 23 are coupled by CO2 welding C and, the first bracket 21, the second bracket 22, and the door frame 1 are coupled by spot welding S.
However, when the door impact beam 10, the first bracket 21, the second bracket 22, and the third bracket 23 are coupled by CO2 welding C, the strength at the welded portion of the door impact beam 10 is decreased by welding heat. In general, the door impact beam 10 requires strength of 1500 MPa or more, but the strength around the CO2-welded portion of the door impact 100 is decreased to the level of 800 MPa, so breaking initiates from the welded portion in a side collision.
Further, when the cross-section of the door impact beam 10 is in the shape of a circle or an ellipse, the sealer 3 disposed between the door impact beam 10 and the external panel 2 is easily separated, so the external panel 2 is not firmly fixed.
Therefore, there is a need for a new door impact beam that can solve the problems of deterioration of strength at a welded portion and separation of a sealer and has a simple configuration without brackets.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to person skilled in the art.